Honda PGM-FI – Programmed Fuel Injection explained

Can you name the first production Honda motorcycle to feature electronic fuel injection technology? If you identified the 1982 CX500TC Turbo, give yourself a pat on the back; you certainly know your Honda family tree. It’s interesting to contemplate that although that particular landmark motorcycle was obviously well-known for incorporating a turbocharger to magnify the power of its 497cc V-twin engine, it was the innovation of its computer-controlled fuel-mixing system that has provided the more lasting impact. While turbochargers quickly reached what seems to be an evolutionary dead-end in motorcycles, today Honda’s Programmed Fuel Injection (PGM-FI) technology has become prevalent for delivery of air/fuel mixture to the engine via high-pressure fuel injectors in a wide assortment of machines: street, dirt and ATV.

So, just how does the Honda PGM-FI system operate; that is, how does the system determine how much fuel it should deliver at the appropriate moment? The key behind this system is the constant monitoring and assessment of engine, atmospheric and riding conditions, and the use of this data to control the quantity of fuel injected into the engine. In technical terms, PGM-FI is an n-alpha mapped injection system. That means the basic variables are the engine speed (n) and the throttle angle (alpha). Based mainly on these two measurements, the system looks to its fuel mapping for the fuel delivery figure corresponding to the n and alpha of the moment.

Next, the engine makes adjustments as needed to this basic fuel delivery figure according to additional variables such as intake-port pressure, engine coolant temperature, intake-air temperature and atmospheric pressure. This process of recalculation of fuel delivery specs is repeated many times per second to ensure the correct mixture is being delivered to meet the existing conditions, and to provide optimal performance and remarkably crisp throttle response over a wide range of operating conditions. This system uses various throttle bodies, digitally controlled injectors and 3-D control maps to meet the differing needs of various models. However, basic operation of the Honda PGM-FI system remains the same for all.